1. Field of the Invention
The invention generally relates to receivers for receiving scanning signals and, in particular, to an apparatus which receives signals having a predetermined time varying format such as a microwave landing system (MLS) receiver for receiving scanning signals provided by an MLS ground system.
2. Description of the Prior Art
The International Civil Aviation Organization (ICAO) has adopted a time reference scanning beam (TRSB) technique as the standard for civil microwave landing systems. MLS ground systems provide elevation (EL) and azimuth (AZ) scanning beams, each including a TO scan followed by a FRO scan, defining the area of coverage of the ground system. An MLS receiver located in an aircraft receives the EL scan and AZ scan and is able to determine the angular displacement of the MLS receiver in the aircraft with respect to the ground system. To do this, it is necessary to establish the centroids of the spatially received signals which result from the swept EL and AZ scanning beams because the azimuth and elevation angles are a function of the time difference between the TO and FRO scans of each beam.